Fibrous membranes with antibacterial activity,were prepared from 10% w/v polyacrylonitrile (PAN) Solutions containing silver nitrate (AgNO3) in the amounts of 0.5-2.5%, by weight of PAN by electrospinning. N,N-Dimethylformamide (DMF) was used as both the solvent for PAN and reducing agent for Ag+ ions. The enhancement in the reduction process was achieved with UV irradiation, which resulted in the formation of larger AgNPs in areas adjacent to and at the Surface of the fibers. Without the UV treatment, the size of the AgNPs was smaller than 5 nm oil average. Under the 10 min of UV treatment, the size of the particles increased with an increase in the initial AgNO3 concentration in the Solutions to range between 5.3 and 7.8 nm on average. Without or with the UV treatment, the diameters of the obtained PAN/AgNPs composite fibers decreased with an increase in the initial AgNO3 concentration in the Solutions, with the diameters of the obtained composite fibers that had been subjected to UV irradiation exhibiting lower values (i.e., 185-205 nm versus 194-236 nm oil average). Both the cumulative amounts of the released silver and the bactericidal activities of the PAN/AgNPs composite fibrous materials against two commonly-studied bacteria, i.e., Grain-positive Staphylococcus aureus and Gram-negative Escherichia coli, increased with increases in both the initial AgNO3 concentration ill the Solutions and the UV irradiation time interval. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1967-1976, 2010